Chrome Version: 68.0.3440.84 (Official Build) (64-bit)
OS: Linux

Visit data:text/html,<meta http-equiv="Content-Security-Policy" content="frame-src 'none';"><iframe src="https://www.canada.ca/content/dam/ircc/migration/ircc/english/passport/forms/pdf/pptc153.pdf">

If you hover over the frame, the message "Requests to the server have been blocked by an extension." (i.e., IDS_ERRORPAGES_SUMMARY_BLOCKED_BY_EXTENSION) is shown. However, as the developer console shows, this was actually blocked due to content security policy, not an extension.

This should be updated to show a more suitable UI string.

Not sure which component this should be (it's CSP affecting the net error code, and then that being reflected in the error page UI).